In the field of mobile communications, research and development on a next generation communication system is rapidly progressing. In the communication system considered as of now, from the view point of broadening the coverage area while reducing PAPR (Peak-to-Average Power Ratio), it is proposed to use a single carrier scheme for uplink. In this communication system, radio resources for both uplink and downlink are properly assigned, as a form of a shared channel which is shared by plural users, according to communication conditions of respective users and the like. More specifically, a data signal of a user in uplink is transmitted on a physical uplink shared channel (PUSCH). The terms “channel” and “signal” may be used synonymously as long as there is no fear of confusion. A data signal of a user in downlink is transmitted on a physical downlink shared channel (PDSCH).
Processing for determining assignment is called scheduling. In order to properly perform scheduling in uplink, each user equipment terminal transmits a reference signal (also called a pilot channel) to a base station and the base station evaluates the uplink channel state based on reception quality of the reference signal. In addition, in order to perform scheduling in downlink, the base station transmits a reference signal to the user equipment terminal and the user equipment terminal reports to the base station information about the channel state (CQIs: Channel Quality Indicators) based on reception quality of the reference signal. Based on the CQIs reported from each user equipment terminal, the base station evaluates the downlink channel state to perform scheduling in downlink. The results of scheduling are transmitted to each user equipment terminal via a downlink control signal. This control signal is called a downlink L1/L2 control signal.
There are two types of uplink control signals: one is control information (called first control information, for the sake of convenience) that should be transmitted together with an uplink data signal and the other is control information (called second control information, for the sake of convenience) that is transmitted irrespective of the presence or absence of the uplink data signal. The first control information includes information necessary for demodulation of the data signal, such as a modulation scheme, a channel coding rate, and the like of the data signal. The second control information includes CQI information of a downlink channel, acknowledgement information (ACK/NACK) of a downlink data signal, information about a resource assignment request, and the like.
When a resource block (radio resource) is assigned for transmitting an uplink data signal, the first control information (and second control information as necessary) is transmitted in the resource block. On the other hand, when the uplink data signal is not transmitted, it is considered that the second control information is transmitted using a dedicated resource (dedicated band). In the following, an example of using the band is described below.
FIG. 1 shows a configuration of an uplink channel. FIG. 1 shows resources (plural resource blocks) for transmitting the physical uplink shared channel (PUSCH) as the uplink data signal, and resources (corresponding to the dedicated band) for a user to which resources for the PUSCH are not assigned to transmit the uplink control signal. The latter is called a physical uplink control channel (PUCCH). In the shown example, one or more of four resource blocks are assigned to users, a first hopping control signal and a second hopping control signal are provided in a certain transmission time interval (subframe), and a third hopping control signal and a fourth hopping control signal are provided in the following subframe. Each hopping control signal corresponds to the PUCCH. By performing hopping with respect to time and frequency in subframes, a greater diversity effect can be obtained. Each of the first through fourth hopping control signals may be occupied by one user or may be multiplexed by plural users. This transmission scheme of uplink control signals is described in 3GPP, R1-071245.